1. Field of the Invention
The present invention relates to a liquid discharge head which ejects (discharges) a droplet to adhere to a recording medium and performs printing, image formation, or the like, and a method of manufacturing the same.
2. Related Background Art
The liquid discharge method (inkjet recording method) includes plural orifices ejecting a liquid such as ink, plural liquid channels which are communicated with each orifice, and plural discharge energy generating elements which are arranged in each liquid channel. The liquid discharge method is one of non-impact recording methods in which ejecting energy is given to the liquid by applying a driving signal to the discharge energy generating element and the printing, the image formation, or the like is performed by ejecting the liquid from the orifice. The liquid discharge method is characterized in that high-speed recording can be performed with a low noise level and fine image can be obtained at a low cost. Further, such kind of liquid discharge method can perform the printing, the image formation, or the like to recording media such as paper, string, fiber, cloth, leather, metal, plastic, glass, wood, and ceramic. The liquid discharge method can be applied to printers as a peripheral of a computer, printing systems such as a copying machine, a facsimile having a communication system, and a word processor, and industrial recording devices combined with various kinds of processing devices, and the liquid discharge method is rapidly becoming widespread in recent years. For such kind of liquid discharge method, there have been proposed and improved various methods in which some of them are available in the market and some of them are under development.
For example, as shown in FIG. 7, the liquid discharge head in such kind of liquid discharge method includes an element substrate 202 having an energy generating element (heating element) 202 which generates the ejecting energy to the liquid, a top plate 203 which has a liquid chamber (not shown) storing the liquid and a liquid supplying port 205 supplying the liquid to the liquid chamber and forms liquid channels 204 by being bonded to the element substrate 201, and an orifice plate 206 having fine orifices 207 for ejecting the liquid.
The top plate 203 is essential to form the liquid channel 204, and the top plate 203 is the important element affecting ejecting performance of the liquid discharge head. That is, various proposals have been made for the top plate 203 of the liquid discharge head, in which good bonding properties and precise structure are required in order to prevent crosstalk of each liquid channel and to keep the ejecting speed constant.
When the top plate is formed by using a silicon material in the prior art, the top plate is produced through a step shown in FIGS. 8A to 8F and 9A to 9F.
FIGS. 8A to 8F show a step of manufacturing the top plate used for a single color liquid discharge head. FIGS. 8D to 8F are sectional views taken on line 8D—8D of FIG. 8A, line 8E—8E of FIG. 8B, and line 8F—8F of FIG. 8C respectively. Thermal oxide films 112a and 112b are formed on a surface on the side where a liquid chamber 115 is formed (hereinafter referred to as liquid chamber surface) and the surface on the side where a liquid supplying port 116 is formed (hereinafter referred to as liquid supplying port surface) respectively in a silicon substrate 111 shown in a chip state. As shown in FIGS. 8A and 8D, patterning is performed to the thermal oxide film 112a on the liquid chamber surface side by photolithography to form a liquid chamber pattern 113. Then, the patterned silicon substrate 111 is etched by an anisotropic etching technique to make a hole through the silicon substrate 111, as shown in FIGS. 8B and 8E. An aqueous TMAH (tetramethyl ammonium hydroxide) solution (for example, TMAH-22 which is a product of Kanto Kagaku) is used as the etching solution for the anisotropic etching, and the through hole is made by the etching though the silicon substrate 111 having a thickness of 625 μm. Then, by removing the thermal oxide films 112a and 112b with wet etching, as shown in FIGS. 8C and 8F, the liquid chamber surface side of the through hole in the silicon substrate 111 becomes the liquid chamber 115, the opposite surface of the through hole becomes the liquid supplying port 116, and a top plate 110 used for the single color liquid discharge head is produced.
FIGS. 9A to 9F show a step of manufacturing a top plate used for a three-color liquid discharge head. FIGS. 9A to 9C are sectional views taken on line 9A—9A of FIG. 9D, line 9B—9B of FIG. 9E, and line 9C—9C of FIG. 9F respectively. The thermal oxide films 112a and 112b are formed on the liquid chamber surface and the liquid supplying port surface of the silicon substrate 111 shown in the chip state. As shown in FIGS. 9A and 9D, the patterning is performed to the thermal oxide film 112a on the liquid chamber surface side by the photolithography to form the three liquid chamber patterns 113. Then, in the same way as described above, the patterned silicon substrate 111 is etched by the anisotropic etching technique to make the hole through the silicon substrate 111, as shown in FIGS. 9B and 9E. Then, by removing the thermal oxide films 112a and 112b with the wet etching, as shown in FIGS. 9C and 9F, the liquid chamber surface side of the three through holes in the silicon substrate 111 becomes the liquid chambers 115, the opposite surface of the three through holes becomes each liquid supplying port 116 which communicates with each liquid chamber 115, and the top plate 110 used for the three-color liquid discharge head is produced.
The high-speed and fine recording is required as recording technology progresses in recent years, so that weight reduction is required and the smaller top plate is formed in the liquid discharge head. In order to be adapted for various kinds of ink, it is necessary not to expose the ink to faces of the silicon as much as possible. Further, it is necessary to provide an alignment mark for performing electric connection and increasing adhesive properties between a liquid supplying member and the top plate, which supplies the liquid (ink) to the liquid chamber in the top plate after the top plate is bonded to the element substrate, to improve prevention of color mixing.
However, as shown in FIGS. 8A to 8F and FIGS. 9A to 9F, in the case of the method in which the liquid chamber is formed on the silicon substrate to form the top plate, the hole of the liquid supplying port is decreased as a size of the top plate is decreased, so that the sufficient amount of liquid can not be obtained for the high-speed printing. When the liquid chamber is enlarged by decreasing the size of the top plate, stiffness of the top plate is reduced, as a result, lifting of the top plate or the crosstalk occurs when the top plate is bonded to the element substrate. Since the pattern can not be formed on an upper portion of the top plate, a problem is created such that the alignment mark for the electric connection and improvement of adhesive properties of the liquid supplying member supplying the liquid can not be also formed. There is also the problem that the ink reacts with the silicon in the case of only the etching plane (111) of the silicon and the silicon is dissolved to generate kogation in the heating element (heater) because the liquid discharge head is used for various kinds of ink.
In the case of a full-line head in which the plural orifices (ejecting port) are arranged over recordable region of the recording medium, since the stiffness of the top plate is reduced, warping is generated between the top plate and the element substrate and the top plate, where the discharge energy generating elements are arranged, which results in displacement between the top plate and the element substrate. As a result, the bonding is not successful and the ejecting performance is affected.